Ursa Major (Sans X Reader)

It had been a couple months since your little sister went missing. Guess how surprised you were to see her on the news with the headline "Young Girl Helps Monsters Escape". When you meet the friends she made in the underground you can help but to love all of them, especially a skeleton with a love for puns and stars.
Sorry I'm not that good at summaries X3
This is my first story so please tell me if I misspelled anything.
I view frisk as a female so I apologize if you view them as male or both.